1. Field of the Invention
The present invention relates to hydraulic couplings used in undersea drilling and production applications. More particularly, the invention involves a locking mechanism for restraining axial movement of male and female coupling members used in undersea applications.
2. Description of the Related Art
Subsea hydraulic couplings are old in the art. Subsea hydraulic couplings are shown, for example, in U.S. Pat. No. 4,694,859 to Robert E. Smith III, and other patents assigned to National Coupling Company, Inc. of Stafford, Tex. The couplings generally consist of a male member and a female member with sealed fluid passageways connecting therebetween. The female member generally is a cylindrical body with a relatively large diameter longitudinal bore at one end and a relatively small diameter longitudinal bore at the other. The small bore facilitates connections to hydraulic lines, while the large bore seals and slidingly engages the male member of the coupling.
The male member includes a cylindrical body having an outer diameter approximately equal to the diameter of the large female bore, and a connection at its other end for hydraulic lines. When the cylindrical body of the male member is inserted into the large bore of the female member, according to various embodiments of the device, fluid flow is established between the male and female members.
The male member and female member are generally connected to opposing junction plates of a manifold and are held together by bolts or hydraulic members attached to the plate. The male member is commonly attached to one junction or manifold plate, while the female member is attached to an opposing plate so as to face the male member and align with it. The male and female members may be attached to the junction or manifold plates using various means such as set screws or threads.
Typically, several subsea hydraulic couplings are grouped together on each junction or manifold plate. For example, between 10 and 30 coupling members may be attached to each opposing plate. In the subsea environment, a diver may be required to connect the opposing plates together, and thereby connect the opposing coupling members on the plates. The coupling members are simultaneously connected and the opposing plates are locked together. U.S. Pat. No. 4,915,419 to Robert E. Smith III, assigned to National Coupling Company, Inc. of Stafford, Tex. discloses a sliding lock plate used for connecting together subsea hydraulic couplings.
Attempts have been made in the past to eliminate or reduce the problems of high separational forces of the couplings due to high pressure in the hydraulic system, by individually locking together the male and female members in each coupling. In the subsea environment, however, individually locking each of the hydraulic coupling members together has been a difficult undertaking.
A proposed solution was the use of lock sleeves for subsea hydraulic couplings. The lock sleeve is pulled back axially to release balls inside the female coupling member. After the male member has entered and seated in the female member, the lock sleeve is released, allowing the balls to reposition in the female and lock the male member and female member together. However, the lock sleeve has a number of disadvantages. It is relatively heavy and bulky, which is undesirable in the subsea environment. Additionally, the lock sleeve requires substantial vertical clearance sufficient to allow for the longitudinal movement necessary for connection or disconnection. Other problems are caused by a build up of silt, ocean debris and marine growth in the lock sleeve. The build up may result in jamming the lock sleeves and especially the locking balls. The couplings require high longitudinal thrust and cannot be disconnected without great difficulty after a period of time subsea.
A reliable solution is needed for locking together subsea couplings that can be easily handled in the subsea environment. In undersea drilling and production applications at increasingly greater depths, it is desirable to connect and/or disconnect the coupling members with robotics or other diverless apparatus. A simple mechanism for connecting and locking together subsea hydraulic coupling members is needed that can be operated without a diver.
In subsea hydraulic applications, remote operating vehicles (ROVs) are needed to grip one of the coupling members (typically the female member) subsea and connect that member to the opposing coupling member. Preferably, the number of different discrete motions required of the ROV should be minimized. Additionally, in order to reduce the complexity of connecting and/or disconnecting coupling members subsea, it is preferable that the ROV connect the couplings in a so-called "one handed" manner by gripping only one of the coupling members, rather than gripping two components such as both coupling members.
It also is desirable to discontinue flow of hydraulic fluid in the coupling by closing the valves in the male and female coupling members, without disconnecting and retrieving one set of members (i.e., the female coupling members). For example, because of adverse weather conditions, strong currents and potential damage to the hydraulic system, it is necessary to shut off the flow of hydraulic fluid to prevent leakage and ensuing damage to the subsea environment. Rather than retrieve the female coupling members while the male coupling members remain subsea, a reliable solution is needed for temporarily "parking" the female coupling members subsea when the valves in the coupling are closed.